An accurate assessment of barometric pressure (BP) may be beneficial for improved operation of a vehicle. For example, diagnostic functions and engine strategies benefit from having an estimate of barometric pressure.
One approach to infer BP from existing sensors on the vehicle equates intake manifold pressure, if available, with barometric pressure during engine stopped conditions. In another example, correlations between throttle position, engine mass-airflow, and barometric pressure can be utilized in cooperation with engine breathing data.
The inventors herein have recognized various issues with such approaches, particularly in the context of a hybrid-electric vehicle. For example, the vehicle may operate for extended periods in an engine-off mode, yet without a manifold pressure sensor, and thus accurate estimates of barometric pressure are unavailable. This problem is exacerbated if the vehicle is descending a hill, as the engine is likely to be off for a majority of such a descent. Further, even when operating, the operating conditions may be ones that correlate only loosely with BP, thus providing low accuracy due to the particular speeds and loads at which the engine operates in a hybrid-electric vehicle.
Such issues may be addressed, in one example, by a vehicle method, comprising: adjusting engine operation responsive to barometric pressure, the barometric pressure based on a pressure change in a sector of the fuel system when the sector is sealed with the vehicle travelling. The pressure change in the sector of the fuel system may be a gauge pressure inside the sealed sector measured by a gauge pressure sensor. In this way, it is possible to utilize a pressure change at the sealed sector of the fuel system, such as a sealed fuel tank, to identify barometric pressure, even with the engine off for extended durations of vehicle travel. In one particular embodiment, the fuel tank acts as a sealed vessel and the external pressure change can be identified by the change in the gauge (relative) pressure inside the fuel tank, since the fuel tank itself is sealed. As such, in a hybrid-vehicle application, during hill descents in which the engine is maintained off, barometric pressure can still be updated. Additionally, during high climbing, the engine is operated and the fuel tank may be unsealed, yet again barometric pressure can be identified through the engine mapping via mass air-flow and throttle position, for example.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above of in any part of this disclosure.